Q 01/05

The skin is the largest organ of the human body. Roughly what share of body mass does it make up?

A) About 16%

B) About 20%

C) About 30%

D) About 45%

Answer · why

A) About 16%

An average adult's skin covers 1.5 to 2 square metres.

Q 02/05

What are the three primary layers of the skin, from outside in?

A) Dermis, epidermis, hypodermis

B) Epidermis, dermis, hypodermis

C) Cuticle, cortex, medulla

D) Stratum, cortex, subcutis

Answer · why

B) Epidermis, dermis, hypodermis

The hypodermis is more commonly called the subcutaneous layer.

Q 03/05

Which of these does the epidermis lack entirely?

A) Melanocytes

B) Blood vessels

C) Keratinocytes

D) Nerve endings

Answer · why

B) Blood vessels

Its deepest cells are fed almost entirely by oxygen diffusing from the surrounding air.

Q 04/05

Which cells produce the pigment melanin?

A) Keratinocytes

B) Melanocytes

C) Merkel cells

D) Langerhans cells

Answer · why

B) Melanocytes

A single square inch of skin holds around 60,000 of them.

Q 05/05

Melanin is made through a process that begins with the oxidation of which amino acid?

A) Tryptophan

B) Glycine

C) Lysine

D) Tyrosine

Answer · why

D) Tyrosine

Eumelanin gives brown-black tones and pheomelanin the red-yellow ones.